Devices of this type are known in the prior art and are used particularly by electricians. One of these devices is represented in FIG. 5.
The device for selection of the variable to be measured is generally a mechanical rotary selector arranged on the front of the instrument, allowing one to select the variable and, for each variable, the measurement scale.
The rotary selector typically has 11 positions defined by stop notches of the selector, which can be accessed successively by turning the selector in an obligatory direction starting from a stop position.
The quality of this selector is one of the important elements of the multimeter appreciated by the user.
Mechanical rotary selectors wear out quickly under the effect of the movement and friction of the brushes against the electrical contacts. This results in wear and tear on the brushes, the contacts, and the housing in which the selector turns. This combined wear and tear causes, over time, measurement drift due to the effect of resistance of the contacts and to the metal deposits on the printed circuits.